UPDATE: At 11:27 p.m. EST on Tuesday, NASA astronaut Scott Kelly and cosmonauts Mikhail Kornienko and Sergey Volkov safely landed in Kazakhstan as scheduled. Kelly and Kornienko had spent a total of 340 days in space as part of the International Space Station's one-year experiment.
ORIGINAL: U.S. astronaut Scott Kelly and his Russian crew mate ended an unprecedented 340-day stay aboard the International Space Station Tuesday and are headed toward a parachute landing in Kazakhstan.
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"It's a little bittersweet," Kelly, 52, said as he turned over command of the orbital outpost to NASA astronaut Timothy Kopra, one of three men remaining on the station.
Kelly and station flight engineer Mikhail Kornienko blasted off for the first year-long stay in the station's 15-year history on March 27, 2015. They worked with eight different crewmates during their 340-day mission, a record for a U.S. spaceflight.
Accompanying Kelly and Kornienko for the 3.5 hour ride back to Earth is Russian cosmonaut Sergey Volkov, who has been aboard the station since September. Their Russian Soyuz capsule is due to make a parachute landing in Kazakhstan at 11:25 p.m. EST.
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NASA and its partners decided to fly two crewmembers for a year on the station as a pilot program to prepare for eventual human missions to Mars lasting at least two years. Typically, crews serve aboard the station for about six months.
Kelly's spaceflight eclipses a 215-day U.S. record set in 2007 by another space station crewmember, Michael Lopez-Alegria.
The Russians, however, remain the long-duration spaceflight champs, with four Soviet-era cosmonauts spending more time in orbit than Kelly and Kornienko. The world record for the single longest spaceflight is a nearly 438-day mission by cosmonaut Valeri Polyakov, who lived on the now-defunct Soviet Mir space station from January 1994 until March 1995.
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After an initial round of medical checks in Kazakhstan, Kelly is to be flown back to the Johnson Space Center in Houston for a reunion with his family and friends. During his final inflight press conference last week, Kelly said the first thing he planned to do was jump in his swimming pool.